In plate-type industrial liquid filters, a plurality of plate elements are arranged in a horizontal stack and controlled for up and down movement by a jack mechanism. When the plates are pressed together, a sheet of filter media is provided between each pair of adjacent plates. A compartment for receiving dirty liquid is formed above each filter media sheet, and a compartment for trapping and removing clean liquid is provided below each sheet. When the plates are separated by the jack mechanism, the sheets of filter media with accumulated solids or cake are advanced in one direction so that the used media and the filter cake on each sheet can be removed, and new media can be put in place for the next filter cycle. Normally, the filter media is supplied in rolls located on one side of the stack of plates and a mechanism for moving or advancing the sheets of filter media is provided on the other side of the plate stack. In my U.S. Pat. No. 3,608,734, a plate-type filter utilizing a prior form of sheet media puller is described. This prior sheet media moving device utilized a multiplicity of sharp pins which were adapted to punch through the sheets of filter media in order to grip the sheets and move them forwardly. For each sheet, a series of pins connected to mounting bars were provided, and each mounting bar was attached to an endless chain that moved the bar downwardly, then forwardly, then upwardly and then back to a starting point for each advancing cycle. Although highly successful for many forms of sheet filter media, the aforesaid pin-type extractor was less effective for thinner forms of filter media which was necessary or more desirable for certain filtering operations. One inherent disadvantage with such prior extractors was that the pins necessarily pierced the filter media in use, thereby preventing its reuse which would otherwise be possible in some cases. Also, the pin-type extractor system heretofore devised was relatively expensive to manufacture since the pins themselves were machined and individually installed and the support plates for the filter were required to be slotted to accommodate the movable pins as they advanced the media. In some instances the pins became bent with use and caused maintenance problems.
A general object of the present invention is to provide an improved filter media extractor for plate-type filters that eliminates the need for pins that penetrate the media.
Another object of the present invention is to provide an improved filter media extractor for plate-type filters that moves each of a plurality of media sheets by providing a surface contact on each sheet that produces a friction factor sufficient to move the filter media forward.
Another object of the present invention to provide an improved filter media extractor for plate-type filters that is more economical to construct and easier to maintain.
Still another object of the invention is to provide a sheet media extractor for plate-type filters that operates effectively with a wide variety of sheet filter media including relatively thin and inexpensive paper media.